Although today’s Royal Wedding went off without a hitch, security concerns are growing about Queen Elizabeth II’s planned trip to the Republic of Ireland next month.

A dissident IRA group, called “Oglaigh na hEireann” or “Real IRA” has warned that the Queen is not welcome on Irish soil and is branding her a “war criminal.”

Elizabeth is expected to make a historic three-day journey to Ireland -- the first by a ruling English monarch in 100 years -- on May 17-20. Her grandfather George V visited Ireland in 1911 when it was still part of the United Kingdom. Since 1921, when Ireland became independent, no British monarch has visited the republic.

Real IRA is among various splinter groups that reject the peace process in Northern Ireland and recently killed a police officer in Omagh, Ulster with a car bomb.

The mainstream, or Provisional, IRA, has already declared a cessation of its hostilities and armed struggle against the British.

Observers fear that these dissident groups will accelerate their campaign of violence.

Oglaigh na hEireann urge all self-respecting Irishmen and women to resist the upcoming insult that is the visit of a British monarch to Irish soil, a member of the group reportedly told a crowd in Derry.

The queen of England is wanted for war crimes in Ireland and not wanted on Irish soil. We will do our best to ensure she and the gombeen [moneylender] class that act as her cheerleaders get that message. Those who think they are serving their community are in fact serving the occupation, and will be treated as such.

The man, who threatened to kill more police officers regardless of religion. added the IRA, in cooperation with others, will continue to resist the occupation to the best of our ability. Victory to the IRA!

Two years ago, Real IRA insurgents murdered two soldiers in Antrim County and exploded a bomb in Derry last year. They also reportedly took credit for a bomb explosion in Omagh in 1998, which killed 29 people.

According to a report on ABC News, senior British security officials that they have concrete intelligence that Irish Republican terrorist groups are seeking to expand their operations onto British soil, including engineering attacks in London itself.

The threats come after a senior Irish Republican politician described Queen Elizabeth as a “legitimate target” of violence.

Josephine Hayden told reporters she “wouldn't have any problem” is a sniper shot the visiting royal party in Dublin.

“I think it would be justified, most definitely, because she [the queen] is the chief of staff of the British armed forces, who are still occupying our country, who are still operating on Irish streets in the six counties of Ulster,” she said. “You might say that she is just a little old grandmother, but it is what she represents, what she symbolizes, that counts. She is a legitimate target, yes.”

The fears are not unfounded. Irish terrorists have threatened British royals before, sometime with resounding success. In 1979, Lord Louis Mountbatten, the uncle of Prince Philip, (Queen Elizabeth’s husband) was killed in county Sligo in an attack organized by the IRA.